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 A325392 Number of permutations of the multiset of prime factors of n whose first part is not 2. 2
 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 2, 0, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 0, 2, 1, 2, 3, 1, 1, 2, 1, 1, 4, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 1, 3, 2, 1, 2, 1, 1, 6, 1, 1, 3, 0, 2, 4, 1, 1, 2, 4, 1, 4, 1, 1, 3, 1, 2, 4, 1, 1, 1, 1, 1, 6, 2, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,15 LINKS FORMULA If n is odd, a(n) = A008480(n). If n is even, a(n) = A008480(n) - A008480(n/2). EXAMPLE The a(90) = 9 permutations of {2,3,3,5} not starting with 2:   3 2 3 5   3 2 5 3   3 3 2 5   3 3 5 2   3 5 2 3   3 5 3 2   5 2 3 3   5 3 2 3   5 3 3 2 MATHEMATICA primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]]; Table[Length[Select[Permutations[primeMS[n]], #=={}||First[#]>1&]], {n, 100}] CROSSREFS Number of times n appears in A325390. Cf. A008480, A056239, A112798, A325327, A325362, A325364, A325367, A325403, A325407, A325460, A325461. Sequence in context: A249147 A260648 A127242 * A025853 A228247 A025847 Adjacent sequences:  A325389 A325390 A325391 * A325393 A325394 A325395 KEYWORD nonn AUTHOR Gus Wiseman, May 02 2019 STATUS approved

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Last modified January 28 00:32 EST 2020. Contains 331313 sequences. (Running on oeis4.)